The United States has released a videotape that it says provides compelling evidence that Osama Bin Laden was behind the 11 September attacks on New York and Washington.

I was thinking that the fire from the gas in the plane would melt the iron structure of the building and collapse the area where the plane hit and all the floors above it only. This is all that we had hoped for

Osama Bin Laden

In the hour-long video, Bin Laden is shown joking and laughing with friends and associatesabout the suicide plane attacks on New York's World Trade Center, in which more than 3,000 people died.

Relaxing in green military jacket and white head-dress, Bin Laden claims to have known the attacks would take place five days in advance, and says the destruction of the twin towers exceeded his expectations.

American intelligence officers are said to have recovered the tape from a house in the eastern Afghan town of Jalalabad following the collapse of the ruling Taleban, who were harbouring Bin Laden.

The tape has flashed round the world

The recording is of very poor audio and visual quality, and Pentagon officials asked four non-government Arabic speakers to listen to the remarks and agree on a uniform translation.

The tape is being seen by America's allies as vindicating the US-led military campaign in Afghanistan.

Bin Laden identifies Mohamed Atta, suspected of hijacking the first plane, as the group's leader.

In one section of the videotape, the Saudi-born militant suggests that some of the hijackers did not know what their mission would be.

"The brothers who conducted the operation, all they knew was that they have a martyrdom operation and we asked each of them to go to America, but they didn't know anything about the operation, not even one letter," he said.

They were overjoyed when the first plane hit the building, so I said to them: be patient

Osama Bin Laden

Bin Laden is seen in the video with the number two in the al-Qaeda network, Ayman al-Zawahri, and a spokesman, Abu Ghaith, in what the Pentagon says is a guest house in Kandahar, in southern Afghanistan.

Bin Laden said that before the attacks on the World Trade Center, he and his men were estimating how many people would be killed.

"We calculated that the floors that would be hit would be three or four floors," he said, gesturing with his hands to show a building and a plane flying into it.

"I was the most optimistic of them all," he said.

He also claimed to have known the attackers were ready.

He appears, if you can believe it, happy, comfortable and joyous with the fact that he was able to take lives

Ari FleischerWhite House spokesman

"We had notification since the previous Thursday that the event would take place that day," he said, chuckling.

He then described hearing the news reports with his aides.

"They were overjoyed when the first plane hit the building, so I said to them: be patient," he said with a smile.

The BBC's Katty Kay says the White House hopes the video will bolster international support for the war on terrorism.

"For those who see this tape, they'll realise that not only is he guilty of incredible murder, he has no conscience and no soul, that he represents the worst of civilisation," said President George W Bush.

'Twisted and sick'

US Senator Ron Wyden, who has also seen the tape, says he hopes it will remove suspicions in countries such as Pakistan that the 11 September attacks were an Israeli plot aimed at drawing the US into a war with Islamic countries.

"This video will open a lot of eyes," Mr Wyden said. "The world will see that you are dealing with a level of pathology... that is very, very twisted and sick."

Bin Laden has used videos to spread his anti-US views

British Foreign Secretary Jack Straw said: "By boasting about his involvement in the evil attacks, Bin Laden confirms his guilt."

A leading Saudi dissident in London, who asked not to be named, said he was sure the recording was genuine because of the language used and topics discussed.

And in the United Arab Emirates, Information Minister Sheikh Abdullah bin
Zaid al-Nahayan said: "There is no doubt in my mind that Bin Laden was behind
those operations. The tape confirms that in a way that leaves no
room for doubt."

But the BBC's Middle East correspondent, Frank Gardner, says that at street level in the Arab world, many believe the tape is a fake, a PR gimmick dreamed up by the US administration.

And the defence minister of the ousted Taleban regime in Afghanistan told the BBC that he was doubtful about its authenticity, saying it was unlikely that Bin Laden would have been naive enough to say such things on a recording.